Electrical cryptograph



March 17, 1959 w. F. FRIEDMAN ELECTRICAL CRYPTOGRAPH 4 Sheets-Sheet 1Filed Aug. 11, 1944 MN 4 M a 7 W e F M M L l W dwsw m-L12.

March 17, 1959 w. F. FRIEDMAN 2,377,555

ELECTRICAL CRYPTOGRAPHJ Filed Aug 11. 1944 4 Sheets-Sheet 2 March 17,1959 w. F. FRIEDMAN ELECTRICAL CRYPTOGRAPH 4 Sheets-Sheet I5 Filed Aug.11. 1944 WILLIAM E FRIEDMAN AT TORNE Y March 17, 1959 w. F. FRIEDMAN2,877,565

ELECTRICAL CRYPTOGRAPH Filed Aug. 11, 1944 4 Sheets-Sheet 4 FIGURE 8FIGURE 9 WILLIAM E FRIEDMAN INVENTOR ATTORNEY United States PatentELECTRICAL CRYPTOGRAPH William F. Friedman, Washington, D. C.

Application August 11, 1944, Serial No. 549,086

8 Claims. (Cl. 35-4) (Granted under Title 35, U. S. Code (1952), see.266) The invention described herein may be manufactured and used by orfor the Government for governmental purposes, without the payment to meof any royalty thereon.

This invention relates to a device or machine, which may be used eitheras a cryptograph for enciphering and deciphering communications, or asan authentograph for testing the authenticity of messages.

The primary object of this invention is to provide a cryptograph orcipher device which is simple in construction and maintenance, butnevertheless affords a high degree of security, is light and readilyportable, and can be readily dissassembled and rearranged to vary thecipher keying elements.

Another object of this invention is to provide an authentograph, thatis, a device for testing the authenticity of a message or signal,thereby providing means for assuring that such a message or signaloriginated at an authorized source and is to be considered authentic.

An additional object is to provide a novel keyboard for use with acryptograph and an authentograph.

Another object is to provide a novel method for the authentication ofmessages.

Other objects of the invention will become apparent from a reading ofthe following specification and claims.

In the drawings:

Figure 1 is a top or plan view with the covers closed.

Figure 2 is a top or plan view on an enlarged scale with the keyboardcover and parts of the rotor cover omitted.

Figure 3 is a side elevation with the covers closed.

Figure 4 is a cross section on line 4-4 of Figure 2 with the rotor coveromitted.

Figure 5 is a perspective view of the rotor latch.

Figure 6 is a perspective view of the rotor actuating mechanism.

Figure 7 is a diagram showing schematically the electric circuits andthe mechanical operating mechanisms.

Figure 8 is a view of a portion of the device, illustrating a modifiedkeyboard and switching means.

Figure 9 is a view of a rotor such as is used in the device of thisinvention.

The embodiment of the invention selected from among others forillustration in the drawings and description in the specification is asfollows. Referring to Figure 7, the device will be seen, in general, toconsist of a source 10 of electricity, connected to a pair of wires 11and 12 across which are connected a plurality (in this instance,twenty-six) indicators 13A, 13B, 13C, etc. These indicators areillustrated as being electric lamps arranged beneath a keyboard andindicator panel 14 (see Figure 2) and each arranged to illuminate oneperforation closed by a transparent cover 15 hearing one letter 16 ofthe alphabet thereon. Panel 14 is secured in place over a gasket 14 ofsoft rubber or the like by means of screws as 14". Across lines 11 and12 are also connected manually operable switches 17A, 17B, 170, etc.,each in series 2,877,565 Patented Mar. 17, 1959 with one of theindicators 13A, 133, etc., arranged for operation by pushbuttons 18projecting through keyboard 14 in proximity to the covers 15.

Connected to each of the indicators 13A, 138, etc., is a multicontactelectric switch, generally indicated as 19. It comprises a number ofrelatively juxtaposable and rotatable cryptographic switching wheels orrotors, 19A, 19B, 19C, and 19D, in cascade, each rotor having aplurality of spring input and output contacts 19' thereon (see Figure9), and a final wheel 19E, which may hereinafter be called thereflecting rotor or reflector, the output contacts of which areconnected in pairs, as shown diagrammatically at 20' in Figure 7. Eachelectrical path, as 20, through the rotor system 19 leads from onestationary contact 20 through the cryptographic rotors, and back,through 20', to another stationary contact 20". These paths or circuits20 are rearranged each time one of the rotors is turned.

In conductor 11 there is a normally'closed electric switch 21. Betweenone of the indicators, in this case 1315, and multi-contact switch 19,there is a normally closed electric switch 22. In parallel with wire 11is wire 11A containing an authenticating switch 23 having an operatinghandle 24. Wire 11A also contains a normally-open switch 25.

Turning now to Figures 1, 2 and 3 for a disclosure of the mechanicalfeatures of the invention, the device is shown as enclosed in a casing26 to which are hinged or otherwise attached a back cover 27 and a frontcover 28.

The front cover, protecting the keyboard, is secured to casing 26 bymeans of a double hinge 28', 28". This arrangement permits the cover tofit snugly upon gasket 14'. thereby to provide a substantiallydust-proof and water-proof closure for the keyboard 14, and yet permitsit to lie flat in front of the machine or to be folded therebeneath. Theback part of the casing 26, adjacent the rotor assembly, is providedwith a lip 26' (see Fig ure 2). Back cover 27 is adapted to fit overthis lip, and has a gasket 27, which provides, upon closure of the backcover, a dust-proof and moisture-proof seal. The front and back coverswhen closed are secured by means of hasps 23' and 23", respectively.

In the top of casing 26 there is an opening 29 through which a counter30 is visible. As is most readily seen in Figure 6, casing 26 has twoprojecting walls 26A and 263, which are supported and strengthened by arod 26C. The cryptographic switching assembly 19 is retained betweenthese walls by a mechanism which will now be described. Wall 26A has anorifice therein through which may be pushed pin 30A having a knurledhead 31 (Figure 2) and a latch 32 cooperating with a retaining spring33. Also pivoted on wall 26A is a spring latch 34 of U-shape, one armbeing bent back parallel to the other. The free end 34A of latch 34 isperforated to allow pin 30A to pass through it and bears cam surfaces 35thereon. Stationary cam 36 has a surface complementary to cam surfaces35 so that when latch 34 is moved from the substantially horizontalposition, in which it is shown in Figures 2, 4, and 6, into the verticalposition, in which it is shown in Figure 5, the free end 34A of latch 34is moved away from wall 26A and compresses the entire rotor-reflectorassembly so as to insure good contacts through the spring contacts 19'thereof.

The manually operated means for rotating the cryptographic rotors 19will next be described. As seen in Figures 1, 2, 3, and 6, casing 26 hasa recess 37 in its top into which fits a plunger consisting offingerpiece 38 having a sliding fit in the recess and a rod 39 uponwhich the fingerpiece is mounted. Rod 39 causes U-shaped stirrup 40 toturn on its pivots in walls 26A and 268. On stirrup 40 is a cam 41,which actuatesfollower 42 fast on shaft 43 of counter 30. Stirrup 40also has a member 44 to which spring 45 is attached and which carriescam face 46. Detent 47 is pivoted at 48 in walls 26A and 26B and isstressed by spring 49 so that cam 50 engages cam face 46. Spring detents60 normally hold rotors 19 in their relative positions but allowmovement of these rotors under the actuation of pawls 58. Detent teeth51 are moved in and out of the ratchet depressions in the surface of therotors 19 upon each movement of stirrup 40, as will be hereinafterfurther described.

Stirrup 40 carries a pin 52 on which are pivoted a plurality ofcam-and-pawl devices, 53A, 53B, 53C, and 53D, which are urged by springs54 against the rotors (see Figure 9). Device 53B, for example (Figure6), has a earn 553 and a pawl 58B, and these are adapted to co operate,respectively, with ratchet depressions 56 of rotor 19A and pawl notch55D on the rotor 19B.

The operation of this device is as follows: Cover 28 is opened to exposethe keyboard 14. If, as frequently happens, limitations of spacerequire, the cover may be folded back beneath the machine. Forenciphering or deciphering, handle 24 is operated so that switch 23 isopen. That push button 18 which is associated with the desired letter isdepressed and the switch controlled thereby is operated. For example (toencipher the letter B), if push button 18 associated with the letter Eis depressed, switch 17E (Figure 7) is thereupon closed, and connectionis made from battery through line 11, switch 21, line 118, switch 17E,lamp 13B, and line 12 back to source 10, illuminating lamp 13E. Thisaction also closes connections from battery 10 through lines 11, 11B,through switch 17E, then along line 110, through switch 22, line 20,thence through rotors 19A, B, C, D and reflector 19E, rotors 19D, C, B,A, to line B, lamp 13Z, thence through line 12, back to source 10. Lamps1312 and 132 are simultaneously lighted, and this indicates that thecipher equivalent of the letter E is Z. To decipher the letter Z, thepush button 18 associated with the letter Z is depressed and the circuitis as follows: battery 10, line 11, switch 21, line 11D, switch 172,line 20B, through the rotor-reflector assembly, line 20, switch 22, line11C, lamp 13E, line 12, back to battery 10. Lamp 13E would beilluminated, giving E as the plain-text equivalent of Z. At the sametime the lamp 132 would also be lighted by the closing of switch 172 andby a circuit which is essentially similar to the one described inconnection with the closing of switch 17E. Thus, since rotors 19 connectall the lamps 13A, 13B, etc., and all the switches 17A, 17B, etc.,together in pairs, each letter has another corresponding to it.

For rotating the cryptographic rotors 19 and thus varying theconnections between the various pairs of lamps 13 and switches 17, theplunger 38 is depressed, stirrup is rotated about its pivots and themembers 53A, etc., moved. A pawl 58 will normally ride on a rim 57 of arotor, and, under these conditions, its associated cam face 55 cannotenter a ratchet depression to step an adjoining rotor notwithstandingthe urging of its spring 54. As soon, however, as a pawl falls into apawl notch 55D it and its cam member move upwardly somewhat and towardthe rotors and the latter engages a ratchet depression. Then, onmovement of stirrup 40, the rotor in question is stepped. It will benoticed that, in view of the manner in which tang 59 of device 53Aunderlies device 53B, etc., device 53A cannot move upwardly unlessdevice 53B has so moved. The pawl member of device 53D rises on eachoperation of stirrup 40, as it drops over shoulder 58' of member 60'.The result is that rotor 19E steps each time the stirrup 40 moves, rotor19D steps once for each revolution of 19E, 19C steps once for eachrevolution of 19D, etc.

It is, in other words, the cam face 55 engaged in a peripheral slot 56and impelled by rotary motion imparted to it by plunger 38-39 whichactually serves to step the rotor. The cam face cannot, however, enterinto one of the notches until the cooperating pawl enters an auxiliarynotch 55D.

Whenever a cam 55 drops into a notch 56, and the movement of the plunger39 is completed, the corresponding rotor 19 is moved one step. Thisre-arranges the connections through the rotors and connects differentpairs of lamps 13A, etc., together. Counter 30 is moved one numeralbecause follower 42 is depressed by cam 41 and spring returned. Detent47 prevents overstepping of the rotors 19 because teeth 51 enter notchesin rotors 19.

A detailed description of the operation of the device as anauthentograph for insuring the authenticity of a message or a signalwill now be given. Assuming that agreement has been previously reachedby the two parties concerned as to the wiring of the several rotors andtheir arrangement in the device, the counter is set to zero, and switch23 is closed by snapping handle 24. Plunger 39 is then depressed,opening switches 21 and 22 and closing switch 25. This movement movescounter 30 one position forward and also one or more rotors 19 one step.The following circuit is then established: Source 10, line 11, line 11A,closed switch 23, closed switch 25, line 20, thence through the rotorsystem to whichever lamp happens to be paired with lamp 13E at themoment. Suppose it to be K. The circuit to lamp 13E is at this time openat switch 22 so that lamp E is not illuminated but only the lampcorresponding to its enciphered equivalent, namely K. The letter whichis thus paired with 13E becomes an authenticator, which will, of course,be duplicated on a machine similarly set to the same key.

Now suppose that the device is being used to authenticate aplain-language message sent from station A to station B. Havingtransmitted the message, station A operates its device and finds theauthenticating letter to be K, for example. This letter is transmittedas the authentication; station B, operating its device, finds that K iscorrect and hence is warranted in its belief that the message comes froman authorized source. Upon the next authentication, the letter will bedilferent, since one or more of the rotors will have been advanced onthe operation of the plunger 38.

To remove the rotors 19, cover 27 is opened, latch 34 moved from theupright position of Figure 5 to the horizontal position of Figure 6which allows cam 35 to enter the corresponding groove in stationary cam36. The compression on the rotor assembly is relieved and, when pin 30is removed, the rotors can be readily lifted out. To replace the rotorsthey are merely set in their approximate positions, pin 30 pushedthrough wall 26A up to its head 31, and latch 34 raised. In thepreferred embodiment, the latch, when lowered, extends beyond the end ofwall 26A. It thus prevents the closing of the rear cover 27. Since theback cover should normally be closed, the feature mentioned serves toassure that the latch will be up and the roto-refiector assemblyproperly compressed.

The modification of Figure 8 includes a viewing panel 60, similar inappearance to the viewing panel and keyboard 14 of Figure 2 andsimilarly secured to the machine by screws, as 60'. In place of pushbuttons 18, however, viewing panel 60 is provided with contacts only, as61. These contacts, as shown, consist merely of small circular elementsof conducting material all connected by a common return wire 12 to thebattery 10. With reference to Figure 7, contacts 61 may be considered asreplacing switches 17A, 17E, etc. In place of the push buttons 18, astylus 62 is provided and this may be considered to be connected toconductor 11 of Figure 7. Encipherment or decipherrnent is accomplishedby making contact between stylus 62 and a desired contact 61 on panel60.

The above description is in specific terms, but it is to be understoodthat the invention is not limited to the precise structures and circuitsshown and described. Instead, for the true scope of the invention,reference should be had to the appended claims.

I claim:

1. In a cryptograph having relatively rotatable electric switchesarranged in cascade therein, a plunger arranged for manual operation,means associated with said plunger and cooperating upon depressionthereof with one of said electric switches for angularly displacing thesame, means associated with said plunger and cooperating upon depressionthereof with another electric switch for angularly displacing the sameafter a predetermined angular displacement of said first mentionedswitch, and a brake operable by said plunger through a lost-motionconnection for preventing more than a desired angular displacement ofany switch.

2. The combination with a cryptographic device having a plurality ofelectrical inputs for the characters to be enciphered, a plurality ofelectrical outputs for the enciphered equivalents of said characters, aviewing panel including a lamp for each character, a switch associatedwith each lamp and with a source of current, and a plurality of circuitseach including said source, one of said switches, a lamp associatedtherewith, an input corresponding to the character represented by saidlamp, and a lamp corresponding to the output associated with the lastmentioned input, whereby the closing of one of said switches will lighta lamp representing a character to be enciphered and a lamp representingthe enciphered equivalent of said character.

3. In a keyboard for a device of the character described, a switch foreach character which may be utilized, a push button extending throughthe keyboard and adapted upon depression to close a switch, an indicatorfor each character which may be utilized, each of said indicators beingadjacent to one of said push buttons, and means for connecting saidindicators and said switches whereby depression of a push button willenergize the indicator adjacent thereto and another indicator to showthe enciphered character.

4. In a device of the character described utilizing rotors havingratchet depressions in the periphery thereof and a pawl notch, means forstepping the rotors including a stirrup having a limited rotarymovement, means for normally holding said stirrup in an inoperativecondition, a plurality of cam-and-pawl devices carried by said stirrup,a cam being adapted for cooperation with a ratchet depression of a rotorand a pawl being adapted for coopera tion with a pawl notch of anotherrotor, means for moving said stirrup, means dependent upon said movementfor causing a cam of a cam-and-pawl device to cooperate with a ratchetdepression of a rotor, and means for preventing another cam fromcooperating with a ratchet depression of another rotor unless the pawlof said last mentioned cam-and-pawl device is also cooperating with apawl notch.

5. The invention of claim 4, further characterized by means includingdetent teeth dependent upon movement of said stirrup for moving intoengagement with ratchet depressions of the rotors, thereby to preventoverstepping thereof.

6. The invention of claim 4, further characterized by spring detentsadapted to rest in the ratchet depressions of the rotors to inhibit therotation thereof.

7. In a cryptograph including a source of current, a plurality ofindicating devices, a normally open switch for each said indicatingdevice, a plurality of permutable electric paths interconnecting saidindicating devices in pairs, and means for permuting said paths, twocircuits closable by closing each said switch, one including said sourceof current, the closed said switch, and the said indicating devicethereof, and the other including said source of current, the closed saidswitch, one of said permutable paths, and the interconnected saidindicating device.

8. A cryptograph according to claim 7, further characterized by amanually operable switch, and a further switch having two operablepositions interposed in a selected one of said other circuitsalternatively to connect in its first position the permutable path ofsaid selected circuit to said normally open switch thereof and in itssecond position to connect said permutable path of said selected circuitto said manually operable switch, means operable by said permuttingmeans for causing said further switch to assume its said second positionthereby to close an authenticator circuit including said source ofcurrent, said manually operable switch, said further switch, saidpermutable path of said selected circuit, and the interconnected saidindicating device.

References Cited in the file of this patent UNITED STATES PATENTS1,096,168 Hebern May 12, 1914 1,657,411 Scherbius Ian. 24, 19281,683,072 Hebern Sept. 4, 1928 1,705,641 Korn Mar. 19, 1929 1,733,886Korn Oct. 29, 1929 1,938,028 Korn Dec. 5, 1933

